Field of the Invention
The field of the invention generally relates to medical devices for treating knee osteoarthritis.
Description of the Related Art
Knee osteoarthritis is a degenerative disease of the knee joint that affects a large number of patients, particularly over the age of 40. The prevalence of this disease has increased significantly over the last several decades, attributed partially, but not completely, to the rising age of the population as well as the increase in obesity. The increase may also be due to the increase in highly active people within the population. Knee osteoarthritis is caused mainly by long term stresses on the knee that degrade the cartilage covering the articulating surfaces of the bones in the knee joint. Oftentimes, the problem becomes worse after a particular trauma event, but it can also be a hereditary process. Symptoms include pain, stiffness, reduced range of motion, swelling, deformity, muscle weakness, and several others. Osteoarthritis may include one or more of the three compartments of the knee: the medial compartment of the tibiofemoral joint, the lateral compartment of the tibiofemoral joint, and the patellofemoral joint. In severe cases, partial or total replacement of the knee is performed in order to replace the diseased portions with new weight bearing surfaces for the knee, typically made from implant grade plastics or metals. These operations involve significant post-operative pain and require substantial physical therapy. The recovery period may last weeks or months. Several potential complications of this surgery exist, including deep venous thrombosis, loss of motion, infection and bone fracture. After recovery, surgical patients who have received uni-compartmental or total knee replacement must significantly reduce their activity, removing running and high energy sports completely from their lifestyle.
For these reasons, surgeons are attempting to intervene early in order to delay or even preclude knee replacement surgery. Osteotomy surgeries may be performed on the femur or tibia, in order to change the angle between the femur and tibia, and thus adjust the stresses on the different portions of the knee joint. In closed wedge or closing wedge osteotomy, an angled wedge of bone is removed, and the remaining surfaces are fused together, creating a new improved bone angle. In open wedge osteotomy, a cut is made in the bone and the edges of the cut are opened, creating a new angle. Bone graft is often used to fill in the new opened wedge-shaped space, and often, a plate is attached to the bone with bone screws. Obtaining the correct angle during either of these types of osteotomy is almost always suboptimal, and even if the result is close to what was desired, there can be a subsequent loss of the correction angle. Some other complications experienced with this technique include nonunion and material failure.